一种简单而有效的防止高温光谱实验中显微物镜温度过高的装置:空气吹扫装置

地球内部是一个高温高压环境。温度对于矿物的物理-化学性质有着非常重要的影响。随着温度的升高,矿物的分子振动、弹性模量、地震波波速等诸多性质有可能发生显著的变化,从而对地球内部的相关物理-化学过程产生非常重要的影响。高温谱学研究(如高温红外及高温拉曼)对了解矿物在高温下的物理-化学性质有着非常重要的意义。尽管高温谱学研究中常用的加热台带有冷却装置,能够确保加热台在很高温度下也能正常运转(如1 500℃),然而加热元件在高温下辐射出的大量热量可能使相关光聚焦物镜系统的温度急剧升高,从而造成热损伤,进而限制了高温谱学研究的温度范围。本文的创新点在于为克服这个困难,我们提供了一种简单而有效的防止高温光谱实验中显微物镜温度过高的装置,从而扩展高温谱学研究的温度范围。通过在物镜系统的附近添加了一套空气吹扫装置,加速空气流动而带走多余的热量,从而降低物镜系统的温度。测试表明:尽管这一装置非常简单,但却非常有效;当实验温度为~1 000℃时,物镜下表面的温度由原来的~235℃下降到~68℃。利用该空气吹扫装置,我们对镁橄榄石进行了温度高达~1 300℃的原位拉曼光谱研究,实验结果与其他研究报道的结果一致。这一事实表明,通过添加该空气吹扫装置,高温谱学研究可以比较容易地在超过1 300℃的高温下进行,所用物镜系统基本没有热损伤,从而避免采用能承受更高温度的不同材质的物镜或者运用长焦距物镜的昂贵办法。     

空芯光波导在光谱气敏检测中的应用

空芯光波导(HWG)用于光谱气体检测中,既可以实现光路的传输,又可以充当气体样品池实现长光程高灵敏度测量,具有体积小,响应时间快、成本低、光路稳定灵活等优点。介绍了基于镀银/碘化银的空芯光波导(Ag/AgI-HWG)、光子带隙空芯光波导(PBG-HWG)和基片集成空芯光波导(iHWG)等类型的空芯光波导,并总结了近年来空芯光波导在光谱气敏检测中的研究及进展,梳理了其应用方式及应用领域。研究表明,空芯光波导替代传统的气体池与傅里叶变换红外光谱(FTIR)、激光吸收光谱和拉曼光谱等不同的光谱技术结合已取得一系列成果,且已经应用于环境监测、呼气诊断和工业过程检测和控制等领域。其中,基于中红外激光吸收光谱的空芯光波导传感器组成相对简单,成本较低,与各类光波导的兼容性和环境适应性较强,发展前景较好。总之,随着激光技术、光波导技术和光谱技术的发展,基于空芯光波导的光谱气体检测正在迅速发展,并逐步由实验室走向现场应用。     

Raman Spectroscopy of Biological Tissues

Abstract

We previously published a comprehensive review paper reviewing the Raman spectroscopy of biological molecules. This research area has expanded rapidly, which warranted an update to the existing review paper by adding the recently reported studies in literature. This article reviews some of the recent advances of Raman spectroscopy in relation to biomedical applications starting from natural tissues to cancer biology. Raman spectroscopy, an optical molecular detective, is a vibrational spectroscopic technique that has potential not only in cancer diagnosis but also in understanding progression of the disease. This article summarizes some of the most widely observed peak frequencies and their assignments. The aim of this review is to develop a database of molecular fingerprints, which will facilitate researchers in identifying the chemical structure of the biological tissues including most of the significant peaks reported both in the normal and cancerous tissues. It has covered a variety of Raman approaches and its quantitative and qualitative biochemical information. In addition, it covers the use of Raman spectroscopy to analyse a variety of different malignancies including breast, brain, cervical, gastrointestinal, lung, oral, and skin cancer. Multivariate analysis approaches used in these studies have also been covered.     

Photoacoustic Raman Spectroscopy of Gases

Abstract

Photoacoustic Raman spectroscopy (PARS) [1] is a nonlinear spectroscopic technique based upon the selective population of a given energy state of a system by the process of coherent Raman amplification (stimulated Raman scattering). The necessary conditions for this process are: (1) the transition involving the initial and final energy levels must be Raman-active, i.e., the transitions must involve a change in the molecular polarizability; and (2) the frequency difference of the two incident laser beams must be adjusted to equal the frequency of this Raman-active transition. Since the occurrence of a Raman spectrum depends on a change in polarizability of the molecule and not on the presence of a transition dipole moment, Raman-active transitions can occur for molecules that have no infrared spectrum. This fact makes PARS a particularly attractive analytical technique for studying molecules which have no infrared spectrum The PARS technique was first demonstrated experimentally using     

Calibrating Multichannel Raman Spectrometers

Abstract

Although multichannel Raman spectroscopy has a history of more than a decade [I], it was only recently that the real potential of this technique became fully appreciated. The use of advanced optical multichannel detectors (OMDs) is now bringing about a substantial change in Raman spectroscopy. For example, the application of this technique to short-lived transient species has established a new frontier of Raman spectroscopy known as transient and time-resolved Raman spectroscopy [2]. The technique has made it possible to measure the spectrum even from an extremely weak scatterer like a monolayer film deposited on a substrate [3, 41. A recent experiment on an intact mouse lens [5] demonstrated that only 1 mW laser power with 1 s exposure time is enough to obtain a good quality Raman spectrum of the lens protein, which is of clinical importance for the prevention of cataract formation. A number of stimulating reports are also notable in a variety of fields including chemistry, physics, biology, medicine, and engineering. The advantages of multichannel Raman spectroscopy are manifold.     

Microanalytical nonlinear single-beam spectroscopy combining an unamplified femtosecond fibre laser,pulse shaping and interferometry

Nonlinear vibrational spectroscopy using a single beam of femtosecond pulses from an unamplified fibre laser oscillator is demonstrated. To achieve high spectral resolution and sensitive signal detection with the picojoule pulse energies available, pulse shaping and integrated interferometric detection is employed. The spectroscopic technique used is coherent anti-Stokes Raman scattering (CARS), which yields well-resolved spectra of molecular vibrations in the 100–350 cm^-1 domain of halomethane samples in the liquid phase. We explore the implications of phase control for the interferometric detection of weak signals. The presented combination of a fiber laser, pulse shaping and CARS microspectroscopy is a first example of simplified schemes for compact and robust nonlinear spectroscopic detection and sensing, which is demonstrated exemplarily by on-line monitoring of the chemical composition in a microfluidic flow cell. PACS 42.55.Wd; 42.62.Fi; 78.47.Fg; 42.65.Dr; 82.80.Gk; 92.20.cn     

Applications of Raman Spectroscopy in Agricultural Products and Food Analysis: A Review

Abstract

Raman spectroscopy has been gaining popularity as an analytical tool due to advances in development of Raman spectrometry and the power of personal computers. Due to to its narrow and highly resolved bands, Raman spectroscopy allows for nondestructive extraction of chemical and physical information about samples and aids in rapid on-line analysis without any special sample preparation. In this review, Raman spectroscopic techniques such as dispersive Raman spectroscopy, Fourier transform Raman spectroscopy, surface-enhanced Raman spectroscopy, and spatially offset Raman spectroscopy are briefly introduced. In addition, applications of Raman spectroscopy are explored, within various fields of agricultural products and food, including fruits and vegetables, crops, meat and dairy products, oil, as well as beverages. In addition, some discussion on the importance of Raman spectroscopy as fundamental and applied research of agricultural products and food is provided.     

Applications of Raman spectroscopy in herbal medicine

Raman spectroscopic techniques are a group of chemical fingerprint detection methods based on molecular vibrational spectroscopy. They are compatible with aqueous solutions and are time saving, nondestructive, and highly informative. With complementary and alternative medicine (CAM) becoming increasingly popular, more people are consuming natural herbal medicines. Thus, chemical fingerprints of herbal medicines are investigated to determine the content of these products. In this study, I review the different types of Raman spectroscopic techniques used in fingerprinting herbal medicines, including dispersive Raman spectroscopy, resonance Raman spectroscopy, Fourier transform (FT)–Raman spectroscopy, surface-enhanced Raman scattering (SERS) spectroscopy, and confocal/microscopic Raman spectroscopy. Lab-grade Raman spectroscopy instruments help detect the chemical components of herbal medicines effectively and accurately without the need for complicated separation and extraction procedures. In addition, portable Raman spectroscopy instruments could be used to monitor the health and safety compliance of herbal products in the consumer market.     

Electrophysical properties and structural features of shungite (natural nanostructured carbon)

This paper presents the results of investigations of the electrical conductive properties with a nanoscale locality at nanoampere currents and the results of an analysis of the correlation between the electrical conductivity and structural features of natural glassy carbon, i.e., shungite. The investigations have been performed using atomic force microscopy, electric force spectroscopy, scanning spreading resistance microscopy, X-ray spectroscopic analysis, and Raman spectroscopy. It has been found that there are differences in electrical conductive properties of the structurally similar shungite samples formed under different PT conditions. Based on the analysis of the structural parameters and specific features of the shungite compositions, it has been shown that the effect of intercalation of impurities into boundary layers of graphene sheets has the most significant influence on the electrical and physical properties of the shungites. The differences in types and values of conductivity of the shungite samples are determined by the different degrees of intercalation.     

基于拉曼光谱技术的甲状腺疾病检测的研究

基于光学成像与光谱技术的无损检测是生物医学光学交叉领域研究的重要发展方向。其中拉曼光谱技术可获得检测对象的生化成分的“指纹信息”,被广泛应用于面向生物分子,细胞以及生物组织的检测诊断研究。甲状腺疾病尤其肿瘤的临床检测往往涉及多方法和技术手段的结合,且存在一定的诊断难度,因此发展新的检测技术方法具有重要的意义。首先综述了拉曼光谱技术在甲状腺细胞系的单细胞拉曼光谱检测与分析,然后介绍甲状腺病理组织和甲状腺正常组织的拉曼光谱鉴别诊断(特别介绍了本研究小组开展以银纳米粒子为增强基底的甲状腺离体组织SERS光谱研究情况),以及拉曼光谱技术在甲状腺激素等方面的研究概况。最后简要探讨了拉曼光谱技术在该领域的研究应用前景和发展方向。     

Characterizing variability in in vivo Raman spectroscopic properties of different anatomical sites of normal tissue in the oral cavity

Raman spectroscopy is an inelastic light scattering technique that is capable of probing biochemical and biomolecular structures and conformations of tissue. This study aims to characterize the in vivo Raman spectroscopic properties of different normal oral tissues in the fingerprint region (800–1800 cm⁻¹) and to assess distinctive biochemical variations of different anatomical regions in the oral cavity. A specially designed fiber‐optic Raman probe with a ball lens was utilized for real‐time, in vivo Raman measurements of various oral tissue sites (i.e. inner lip, attached gingiva, floor, dorsal tongue, ventral tongue, hard palate, soft palate, and buccal). The semiquantitative non‐negativity‐constrained least squares minimization fitting of reference biochemicals representing oral tissue constituents (i.e. hydroxyapatite, keratin, collagen, DNA, and oleic acid) and partial least squares‐discriminant analysis (PLS‐DA) were employed to assess the significance of inter‐anatomical variability. A total of 402 high‐quality in vivo oral Raman spectra were acquired from 20 subjects. The histological characteristics of different oral tissues were found to have influence on the in vivo Raman spectra and could be grossly divided into three major clusterings: (1) buccal, inner lip, and soft palate; (2) dorsal, ventral tongue, and floor; (3) gingiva and hard palate. The PLS‐DA multiclass algorithms were able to identify different tissue sites with varying accuracies (inner lip 83.1%, attached gingiva 91.3%, floor 86.1%, dorsal tongue 88.8%, ventral tongue 83.1%, hard palate 87.6%, soft palate 83.3%, and buccal mucosa 85.3%), bringing out the similarities among different oral tissues at the biomolecular level. This study discloses that inter‐anatomical variability is significant and should be considered as an important parameter in the interpretation and rendering of Raman diagnostic algorithms for oral tissue diagnosis and characterization. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy and polarization: Selected case studies

We show, through several selected case studies, the potential benefits that can be obtained by controlling the polarization states of the exciting and scattered radiations in a Raman scattering experiment. When coupled with polarization control, Raman spectroscopy is thus capable of providing extra information on the structural properties of the materials under investigation. The experimental examples presented in this work are taken from the area of both conventional, i.e., far-field, as well as from near-field Raman spectroscopy. They cover topics such as the stress tensor measurement in strained semiconductor structures, the vibration mode assignment in pentacene thin films and the Raman scattering tensor determination from near-field measurements on azobenzene monolayers. The basic theory necessary for modelling the far- and near-field polarized Raman responses is also given and the model efficiency is illustrated on the experimental data.     

姜油细胞原位拉曼光谱研究

提出一种用拉曼光谱原位分析新鲜姜油细胞中姜油主成分的方法。用徒手切片制备新鲜姜样品,该样品置于DXR 激光共焦显微拉曼光谱仪下,用20倍物镜观察到油细胞,将激光聚焦在该油细胞上,获得了姜油细胞中姜油的拉曼光谱,共21条谱峰。不同油细胞上获得的拉曼光谱非常相似。获得了姜精油的拉曼光谱,与姜精油拉曼光谱的37条谱峰比较,油细胞有19条谱峰与之有对应关系。为了解释油细胞精油及姜精油的拉曼光谱,用密度泛函理论计算了姜烯的拉曼光谱。姜精油拉曼光谱有31条谱峰,油细胞中有19条谱峰与计算光谱有对应关系。该研究提供了一种拉曼光谱技术与密度泛函理论计算结合的快速容易的精油质量控制方法。     

In situ Raman spectroscopic monitoring of hydroxyapatite as human mesenchymal stem cells differentiate into osteoblasts

The differentiation of stem cells into specific cell types is playing an essential role in the development of stem cell therapy, tissue engineering, and regenerative medicine. In this research, Raman microspectroscopy was applied to monitor the development of hydroxyapatite [HA, Ca₅ (PO₄)₃ (OH)], which is associated with the differentiation of the human mesenchymal stem cells (hMSCs) into osteoblasts. Raman spectra exhibited dramatic changes in the HA region, 950–970 cm⁻¹, over the period of 7–21 days after the start of differentiation. This work demonstrates the successful application of Raman spectroscopy for monitoring and quantitatively evaluating hMSC differentiation into osteoblasts. Copyright © 2008 John Wiley & Sons, Ltd.     

Vibrational spectroscopic approaches for the quality evaluation and authentication of virgin olive oil

Vibrational spectroscopy as an important branch of molecular spectroscopy has been extensively employed for the analysis of olive oil. To date, plenty of research articles have been published with regards to the analysis of olive oil, which is really a complex matrix, demonstrating the great potential of vibrational spectroscopic approaches in these studies. In this critical review, we cover latest progresses and applications of the three vibrational spectroscopies (mid-infrared, near-infrared, and Raman spectroscopy) used for the analysis of olive oil. In the first part of this review, we focus on the basic theoretical aspects related to vibrational spectroscopic techniques and chemometrics, while in the second part, we discuss their recent applications in qualitative evaluation and authentication of virgin olive oil.     

基于光谱融合的火星表面相关矿物分类方法研究

多源数据融合能在一定程度上扩展数据信息量,更利于建立准确和稳健的分析模型。行星探测中常采用多个载荷协同分析同一目标,因此利用多载荷数据融合辨别分析火星矿物具有重要科学意义和应用前景。分别采用可见近红外(Vis-NIR)反射光谱和拉曼(Raman)散射光谱两种技术手段测量了火星表面主要矿物(硅酸盐、硫酸盐、碳酸盐)的光谱特征曲线,并对获取的光谱数据进行基线校正、Savitzky-Golay平滑以及标准矢量归一化(SNV)等必要的数据预处理。根据光谱特征,首先选取样品Vis-NIR和Raman数据信息丰富、信噪比高、光谱信号重叠小的波段(Vis-NIR：430～2 430 nm,Raman：130～1 100 cm-1),然后运用软独立建模分类法(SIMCA)、主成分分析法-K最邻近分类法(PCA-KNN)分别建立基于Vis-NIR,Raman及两者融合(累加融合、串联融合)的矿物聚类分析模型。采用SIMCA算法的矿物聚类准确率由单一光谱建模的72.6%(Vis-NIR),90.7%(Raman)提升为融合建模的96.3%(累加融合)和98.1%(串联融合);采用PCA-KNN的准确率由单一光谱建模的68.9%(Vis-NIR),72.9%(Raman)提升为融合后的80.3%(累加融合)和92.6%(串联融合)。实验结果表明：光谱融合能够发挥Vis-NIR,Raman各自的数据优势,所建火星表面相关矿物分类模型的预测准确度更高。该研究为我国火星探测任务奠定了岩石分类方法基础。     

KPCA-聚类分析法和用便携式拉曼仪快速鉴别降糖药

对不同种类的降糖药片进行拉曼光谱的核主成分分析(KPCA)-聚类分析,实现快速、简便的鉴别。KPCA可以有效地避免主成分分析(PCA)只能处理线性问题和降维效果不明显的弊端。它通过一个非线性变换,首先将原变量空间映射到高维特征空间,然后在这个高维特征空间中进行线性主成分分析。采集得到的药片拉曼光谱的KPCA-聚类分析结果表明,采用KPCA提取特征变量的聚类结果比采用PCA提取特征变量后进行聚类分析的效果好,并且未经刮除表面包膜的降糖药片识别准确率为96.5%,经过刮除表面包膜处理的降糖药片的识别准确率为100%。便携式拉曼光谱仪结合该方法以其检测速度快、准确率高、使用简便、无样品前处理等显著优势,为药品的快速检验技术提供一种新的有效的鉴别手段。     

Noninvasive molecular identification of particulate matter in lungs by Raman microspectrometry

A new method for the analysis of particulate matter in lungs is proposed. It combines the exhaled breath condensate technique and Raman spectroscopy. The sampling method is noninvasive, which is suitable for the detection of occupational exposure to dust. The chemical composition of dust particles is assessed by Raman microspectroscopy. The effectiveness of this method as a means of identifying markers of occupational exposure to mica dust is evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy can discriminate distinct glioma subtypes as defined by RNA expression profiling

Raman spectroscopy is a molecular spectroscopic technique that can measure the molecular composition of tissue samples within seconds without any extraction processes or dyes. In microbiology, Raman spectroscopy is used to identify bacteriae. In glioblastoma tissue, it was reported that necrosis, normal brain and tumor can be discriminated using Raman spectroscopy. Therefore, we hypothesized that Raman spectroscopy could discriminate glioblastoma tissue from different glioma subtypes defined by RNA expression profiling. We analyzed 20 glioma samples from two distinct molecular subtypes. Both subtypes consisted of glioblastoma samples showing a variety in glioma grading and typing. The Raman spectroscopic results could be grouped in two distinct clusters in an unsupervised cluster analysis. Further analysis of these clusters showed that they were fully congruent with the two clusters as defined by RNA expression profiling. Conclusion: our results demonstrate that Raman spectroscopy can discriminate between different molecular subtypes of glioma and, therefore, may prove to be a valuable tool in in vitro cancer research. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman Spectra of Porphyrins

The spectroscopy of porphyrins has been developing rapidly during the last two decades, this class of compounds being of great biological importance and possessing a number of significant properties. Different spectroscopic techniques, viz., electronic spectroscopy including fine-structure quasiline spectra (Shpolsky effect), infrared spectroscopy, luminescence, flash photolysis, ESR and NMR spectroscopy etc., have been applied to the study of these molecules (see reference ¹ for a review). However until recently there were no publications on Raman spectra of porphyrins and related compounds although it is evident that a complete analysis of molecular vibrations is impossible without knowing the Raman frequencies, especially for centrosymmetrical molecules. We have obtained Raman spectra of two porphin derivatives, viz., copper and nickel octamethylporphin ² which seems to be, together with data on hemoglobin and cytochrome^3-5 and on chlorophylls ⁶, the first observation of Raman spectra of porphyrins. In this paper Raman spectra of several metalloporphyrins are presented including metal complexes of porphin, octamethylporphin, etioporphyrin I, meso-tetraphenylporphin and tetrabenzporphin. For some of them Shpolsky spectra have been obtained and a juxtaposition is made of the two kinds of spectral data concerning the frequencies of molecular no- modss. Also some data of infrared spectra are presented.